Broadband over Power Lines (BPL) is a method of providing
broadband internet access to consumers using High Frequency (HF) radio signals
coupled into the mains power wiring.

In the BPL system, broadband internet signals are modulated at HF and
injected into the overhead power lines. The signals are decoupled from the
power lines at the customer's premises.

The downside of BPL

Of course, power lines are designed for carrying high
voltage AC at 50 or 60Hz, not HF radio signals. BPL enabled power lines
act as large HF antennas, radiating the BPL signals hundreds of metres from the
power lines.

Use of the electricity supply network to convey BPL
signals will result in the leakage of radiofrequency emissions. This leakage has
potential to cause interference to radio communications services.

To achieve the high data bandwidth required for delivery
of broadband internet access, the BPL system uses the HF and low VHF radio spectrum
from 2 MHz to over 35 MHz. The result is that BPL generates wideband noise
over all of HF in the vicinity of the enabled power line. This noise is of sufficient amplitude to mask even
relatively strong HF radio signals

BPL is a problem for all HF users

Some radio professionals have regarded BPL as a problem
primarily for amateur radio operators.

Although the ITU and IEC are
working behind the scenes on BPL, national amateur radio societies like the
Wireless Institute of Australia, the American Radio Relay League and the Radio
Society Of Great Britain have taken a high profile in opposing BPL.

Of course, BPL is a major problem for amateurs, as
they often operate with very weak signals.

However, the wideband nature of BPL means
that its emissions are not confined to the amateur HF radio bands. BPL can
and does radiate signals on maritime, aeronautical, broadcasting, land mobile,
fixed service and military HF allocations.

Some countries (notably Japan) have actually banned BPL
because of its proven interference to HF communications. From a technical
standpoint, BPL is actually a poor choice for distributing high speed internet.
There are more suitable technologies available such as WIFI, fibre and cable.

The situation in Australia

There are a number of BPL trials taking place in Australia
at the moment, with the major one being conducted in the Island State of
Tasmania

The Australian Government Radio Regulator, ACMA, has developed a set
of guidelines for the conduct of BPL trials. These guidelines include the
following provision:

Quote

Access BPL operators have an obligation to undertake
appropriate measures in trialling Access BPL technology to ensure they do not
breach the legal provisions of the Radiocommunications Act.

Particular attention must be given to radio communications
established for safety-of-life services, police forces or for the safe operation
of a vessel or aircraft.

Unquote

The guidelines then go on to list the specific frequencies
to be avoided, including maritime R/T and DSC distress and safety channels.

Unfortunately, monitoring of the
Tasmanian BPL trial has revealed that the system is, in fact, radiating signals
on the 2, 6, 8, 12 and 16 MHz radiotelephone and DSC distress and safety
channels.

These monitoring observations have been passed to the
ACMA. Given the potential threat to safety of life, it is hoped that ACMA
investigate this problem as a matter of urgency.

Obviously, Maritime Distress and Safety channels are
mandated the highest level of protection in the International Radio Regulations,
as these channels are used for safety of life at sea purposes.

Moreover, Section 192 of the Australian Radio
Communications Act specifically prohibits transmissions which may
prejudice the safe operation of a vessel. Heavy penalties are prescribed for
breaches of this Section.

So, what is the issue?

Some may argue that BPL emissions on maritime channels do
not present a problem unless the effected power line passes close to a coast
radio station. However, the fact that these signals are being radiated, in
apparent breach of the Government guidelines, can only lead to speculation as to
the technical capability of the system provider.

If the signals are not supposed to be radiated now, how
can BPL providers guarantee that they will not be radiated from a system which
does pass by a coast radio station?

It will be too late to address this problem when a
distress signal is blocked by BPL....

One wonders what response ACMA will make to a Coronial
inquest into the deaths of mariners who were unable to transmit a distress
signal to shore because of BPL interference....

More information on BPL

There are many web sites dedicated to BPL and its
problems.

Some of the following sites are primarily written from an
amateur radio perspective, however they provide a good technical background on
BPL and its potential for interference with all licensed HF radio communications
services.